Heretofore, for example, in an automated assembly line for automobiles, an assembly process has been carried out in which clamping is performed by a clamp apparatus under a condition in which preformed body panels are positioned in an overlaid manner and the body panels are welded together.
Such a clamp apparatus, for example, as disclosed in U.S. Pat. No. 4,905,973, is equipped with a body, a drive unit which includes a cylinder connected to the body, and a clamp arm that projects externally with respect to the body. In addition, by displacing a piston of the drive unit upon supply of air to the cylinder, a piston rod is displaced together with the piston, whereby the clamp arm, which is connected to a link mechanism constituted from a plurality of arms, is rotated through a predetermined angle. Consequently, a workpiece or the like can be clamped by the clamp arm.